1. Field of the Invention
The present invention relates to laboratory safety enclosures for use in handling biohazard materials, and in particular biological safety cabinets in which the fan is isolated from biohazard contaminated air, without interfering with the flow of uncontaminated air through the work chamber.
2. Description of the Prior Art
Fume hoods and laboratory safety enclosures are safety devices used in research, analytical, teaching, and other laboratories. These containment devices provide enclosed work areas where handling of toxic substances can be performed with minimum risk to users. They are used primarily in pharmaceutical, chemical, biological and toxicological laboratory settings. Biological safety cabinets are particularly adapted to the handling of biologically hazardous materials while providing product and personnel protection. A biological safety cabinet is comprised of a work chamber within which materials are manipulated or worked upon by an operator, a means for introducing uncontaminated air into the chamber, an air exhaust mechanism for removing contaminated air from the chamber, and a HEPA filter for removing hazardous contaminants from the contaminated air before exhausting the air from the cabinet, and/or returning the air to the work chamber.
The work chamber may include a pair of spaced, parallel side walls; rear and upper walls joining the side walls; and a bottom wall or floor that together define the work chamber. The front edges of the side, upper and bottom walls may define an access opening or inlet into the chamber through which the operator manipulates material within the chamber. Exterior air, i.e., air from outside the cabinet, can enter the chamber through this access opening. For example, exhaust ports can be provided in both sidewalls of the cabinet. Air is exhausted from the work chamber through an opening that may be located on the opposite side of the chamber from the access opening or in the bottom of the chamber, preferably front and back, depending on the cabinet design.
Air exhausted from the chamber may be discharged to the atmosphere, i.e., to the exterior of the cabinet, such as into the room where the cabinet is located, or outside the building. Before being discharged, the air is directed through a HEPA filter to remove contaminants. More commonly, a portion of the air is returned to the work chamber after passing through the HEPA filter. Makeup air to replace the portion of the air discharged is then drawn in from the exterior of the cabinet.
Periodic maintenance of the biological cabinet is required. In particular, it is often necessary to repair or replace the fan used to draw contaminated air from the chamber. If there is a risk that the fan has been contaminated with hazardous material, it is necessary to observe hazardous material procedures, which dramatically increases the difficulty and time required for fan repair or replacement. Therefore, a biological safety cabinet design that avoids fan contamination without adversely affecting the desired laminar airflow through the work chamber would be of considerable value. Accomplishment of these objectives while still providing a compact cabinet design would be particularly useful.